Space junk, though invisible to us on Earth, poses a significant danger to both global communications networks and the lives of astronauts. Japan’s space agency has partnered with a fishing equipment company in an effort to rein in some of the orbiting debris. Back in 2011, the Japan Aerospace Exploration Agency (JAXA) joined forces with Nitto Seimo – a fishing equipment company renowned for its durable fishing nets. Together, they have developed a special net that will theoretically be able to capture a portion of the estimated 100 million pieces of man-made trash orbiting our planet. The first test of this high-tech “fishing” gear is scheduled for late February. “[It] will involve launching a satellite into space that will unravel a net about 980 feet long that will create a magnetic field to attract space debris,” wrote The International Business Times. “The net, which is made of three strong and flexible metal fibers, will be in Earth’s orbit for about a year before being pulled down by Earth’s gravity, which will incinerate the captured debris.”

Just how serious is the space junk problem? According to NASA’s Orbital Debris Program, the area of space that exists between 900 and 1000 kilometers from our planet’s surface has already reached “supercritical” debris density levels. That band is a part of what scientists call the Lower Earth Orbit (LEO), where most satellites – as well as the International Space Station – are situated. NASA estimates that a piece of space junk larger than 1 cm in diameter will strike a satellite in LEO every five or six years. “A one-centimeter piece of debris doesn’t sound like much … but orbital speeds in LEO are typically greater than 7 kilometers per second – 30 times faster than a jet aircraft,” said Discovery News. “A speck of paint from a satellite once dug a pit in a space shuttle window nearly a quarter-inch wide.”

In theory, something as small as a metal bolt has the potential to knock out communication satellites (rendering many smartphones useless), satellites used for weather forecasting, GPS systems, and television signals. The floating shrapnel created when two satellites collide could even cause a “chain reaction” that renders some orbits unusable. Large debris could even rip a hole in the space station, putting astronauts’ lives in danger. According to JAXA’s website, the Japanese space program is looking into several other methods for cleaning up space trash. They include an “electrodynamic tether” that would slow down debris enough to make it re-enter the atmosphere and a satellite with ion engines that could use its thruster to knock objects into a lower orbit. An even more far-fetched idea involves a giant “Styrofoam ball, kilometers in diameter” that debris would stick to. If upcoming tests are successful, JAXA’s magnetic garbage net could be deployed as early as 2019.

Japanese space scientists are set to test a tether they hope will help pull junk out of orbit around earth, clearing up tonnes of planetary clutter. Researchers at the Japan Aerospace Exploration Agency (Jaxa) have developed what they called an electrodynamic tether made from thin wires of stainless steel and aluminium. The idea is that one end of the strip will be attached to one of the thousands of dead satellites or bits of rocket that are jamming up space and endangering working equipment. The electricity generated by the tether as it swings through the earth’s magnetic field is expected to have a slowing effect on the space junk, which should, scientists say, pull it into a lower and lower orbit.

Eventually, the detritus will enter the earth’s atmosphere, burning up harmlessly long before it has a chance to crash into the planet’s surface. “The experiment is specifically designed to contribute to developing a space debris cleaning method,” said Masahiro Nohmi, associate professor at Kagawa University, who is working with Jaxa on the project. Nohmi said a satellite developed by the university was expected to be launched into space on February 28, with the tether aboard. “We have two main objectives in the trial next month,” he said. “First, to extend a 300-metre tether in orbit and, secondly, to observe the transfer of electricity.” The actual reeling in of orbiting rubbish would be the objective of future experiments, he said. A spokesman for Jaxa said the agency also planned to conduct its own trial on a tether in 2015. More than 20,000 bits of cast off equipment, including old satellites, pieces of rocket and other fragments are uselessly orbiting the earth in a band 800 to 1,400 kilometres from the surface of the planet at terrific speed. Their presence causes problems for space scientists, who have to try to prevent the space junk from smashing into functioning satellites and damaging parts.

Next month, Japan’s space agency (JAXA) will launch a space trawler — a spacecraft that will drag a giant aluminium and steel net while orbiting Earth, hoping to bag itself some space junk. NASA tracks around 20,000 pieces of larger (5cm+) orbital debris, but there’s an estimated 500,000 pieces of marble-sized, untrackable debris in orbit as well. If a single piece of space junk hits an orbiting, functional spacecraft, the collision is likely to be catastrophic — just like in the movie Gravity — and create more debris in the process. If we don’t get on top of orbital debris now, it’s feared that one day the junk will be so dense that we won’t be able to leave the surface of Earth without being smashed to pieces. Dealing with orbital debris is a relatively new area of research, brought into focus by China’s 2007 anti-satellite missile test, and the 2009 collision of two satellites (one of which had been inactive since 1995; it was space debris). In both cases, huge amounts of orbital debris were created — debris that might then go on to strike other satellites. The International Space Station, because of its size and the fact that it has human occupants, is of particular concern. As you can see in the images throughout this story, there’s a lot of junk out there, and the problem will only get worse unless we do something about it.

Fortunately, most of our space agencies are currently working on some kind of plan to clean up both low Earth orbit (LEO, where most of the junk is) and geostationary Earth orbit (GEO). NASA has toyed with the idea of a “laser broom” — an Earth-based laser that fires up into space, shifting debris that’s on a collision course, or possibly de-orbiting it. Another option is sending up another spacecraft that attaches a small rocket onto the debris, allowing it to guide itself into a safer orbit, or de-orbit in the atmosphere. DARPA’s Phoenix project wants to take small satellites up into space and attach them to old, inactive satellites — the small satellites would use the old satellite’s antennae array, reducing the amount of waste (but not the amount of junk floating around in space).

JAXA’s electrodynamic tether

And then there’s JAXA’s method, which is almost sci-fi in its approach. Basically, the Japanese space agency wants to launch a specialized spacecraft that carries an electrodynamic tether. JAXA teamed up with Nitto Seimo, a fishing equipment company, to create this mesh of steel and aluminium wires. The tether generates an electromagnetic force that pulls space debris towards it. Once the net is full of junk, it de-orbits and burns up in the atmosphere. The first version, which is being launched in February, will be 700 meters long — if it goes well, the next version will be 10 kilometers (6.2 miles) long. JAXA’s net is by no means a sure thing — there researchers who think that the net will get torn up by debris and become space junk itself, or it might inadvertently snag an operational satellite. Proactive measures are being taken, too: satellite makers are increasingly required to include functionality that allows the craft to maneuver into a graveyard orbit (an orbit specifically for debris, so it can’t interfere with operational satellites), or to de-orbit and burn up in the Earth’s atmosphere. If we simply sit back and do nothing, then the scenario predicted by NASA’s Donald Kessler may indeed come to pass. Back in 1978, Kessler proposed that, one day, there would be so many objects in low Earth orbit (LEO) that a few collisions could cause a runaway cascade, with each collision creating yet more debris that would go on to cause more collisions, creating more debris… and so on, eventually rendering space travel and exploration impossible. This scenario is now called the Kessler effect or syndrome. Hopefully our space agencies can club together and sort out our space junk problem before such a scenario occurs, because getting stuck here on Earth would be rather annoying.

Since the birth of space flight in 1957, the number of man-made objects orbiting the Earth has grown every year. There are now more than 15,000 such objects larger than 10cm, at least those that we know of. Even very small particles can pose a risk to spacecraft, because of the high relative velocities at which they travel. Not only can space debris affect critical equipment such as communications satellites, but it can also endanger manned space flights. A dramatic illustration of the dangers of space debris is given in the film “Gravity”. It may have taken some artistic license with science to craft a good story, but its main premise is plausible. What Gravity showed was the worst case scenario, known as the Kessler syndrome, where a collision between two objects generates a cloud of smaller debris, which triggers a chain reaction of further catastrophic collisions, thereby rapidly increasing the amount of debris. This could make the low Earth orbit unusable for spacecrafts.

Most of those are useless fragments of once-useful objects, which were created by explosions, collisions or missile tests. For instance, an accidental collision between the Iridium-33 and Kosmos-2251 satellites in 2009 caused them to shatter into 2,200 (recorded) fragments. Smaller space debris is much harder to track, but NASA estimates that up to 500,000 objects larger than 1cm, and 135 million particles over 1mm in size may now be orbiting the Earth.

Space debris is becoming a serious issue, and many space agencies have started working on solutions. One approach being taken by JAXA, Japan’s space agency, is to use a magnetically charged 700m-wide net made from aluminium and steel wires. If used at the right height it will attract floating space debris to it. When enough has been caught, the system can be ordered to fall out of its orbit back to Earth. During that process the debris, along with the net, will burn up as it enters Earth’s dense atmosphere. JAXA will be doing a test launch of the system next month.

The other approach is to remove existing inactive satellites from orbit. A prime target for this experiment would be the European ENVISAT satellite which stopped functioning in 2012 and now drifts uncontrolled in orbit. At an altitude of 800km and with mass of more than 8,000kg, the ENVISAT satellite would take more than 150 years to deorbit – that is, drop out of its orbit – naturally. Throughout that time the satellite would be at risk of colliding with other objects and generating further debris. A more sustainable solution is to remove future satellites from orbit after they have served their purpose, thereby mitigating the growth of the amount of space debris. This is why international guidelines have been proposed which will restrict post-mission deorbiting time to 25 years for all new satellites.

A gossamer sail deorbiting system deployed from a host satellite. The 5×5 m square sail consists of four quadrants which are supported and tensioned by four diagonal deployable masts.

Most satellites designed today take will take longer to deorbit, and new technical solutions are necessary to meet the guidelines. This is where Surrey Space Centre (SSC) working with the European Space Agency (ESA) have developed a Gossamer Sail for Satellite Deorbiting. The idea is to attach a large and very light, or gossamer, sail to a satellite, which can be deployed after its mission is over. The lower Earth orbit has some atmosphere, which enables the large sail to generate enough aerodynamic drag to slow down and deorbit the satellite more rapidly. Unlike existing deorbiting systems based on chemical or electrical propulsion, the gossamer sail system is relatively simple and does not require propellant or electrical power throughout its deorbiting phase.

The gossamer deorbiting system is designed to automatically orient the sail in the direction where maximum drag can be achieved, ensuring quicker deorbiting. Furthermore, the sail is made reflective, which allows it to make use of the solar radiation pressure to manoeuvre; solar sailing, so to speak. This enables the satellite to be lowered to an orbit where the aerodynamic drag takes over, allowing the satellites to be placed in higher orbits and still meet the deorbiting requirements. Developing and testing the SSC gossamer deorbiting sail was quite an engineering challenge. The 5×5m sail and the four deployable masts that support it have to be packaged inside a space measuring approximately 10×10×20cm. To achieve this, the sail is made of an ultra-thin membrane and the special carbon-fibre masts can be coiled up tightly (much like a tape measure). The SSC gossamer sail is expected to be tested within the next year. After the technology has been successfully demonstrated in space, the system can then be fitted to much larger satellites as an end-of-life deorbiting system. This will provide satellite operators with a means to meet the 25-year deorbiting guidelines, which in turn will help safeguard the possibility of space flight for future generations.

Hundreds of thousands of pieces of spacecraft, satellites and other equipment from human spaceflight zip around our planet, some travelling faster than the speed of sound. According to a report released by the US Congressional Research Service this month, running into even a small piece of junk can be disastrous. An object 10 centimetres across could “catastrophically damage a typical satellite”, it says. One just 1 centimetre across could disable a spacecraft. The worst-case scenario is the Kessler syndrome, proposed by astrophysicist Donald Kessler in the 1970s. Too much trash, he warned, and the pieces would collide with each other, resulting in more and more debris. To build its debris-catching net, JAXA brought in Nitto Seimo, a company that specialises in fishing equipment. Unlike a net you would use in the ocean, this one is a 700-metre-long mesh of aluminium and steel wires that hangs from an uncrewed spacecraft. The net is fitted with sensors that look for light reflecting from small pieces of debris and automatically aligns itself so that it can attract the material. The tether changes its orbit thanks to an electrical current flowing through the wires, which creates an electromagnetic field that attracts the debris and pushes the net away from Earth’s geomagnetic field. Once the net has grabbed enough debris it is ordered to slow down and de-orbit, allowing the debris, spacecraft and net to burn up as they enter Earth’s atmosphere.

JAXA thinks the net’s main advantage is its simplicity – it’s lightweight and doesn’t require any propellant to move. If next month’s test launch goes well, it plans to build a 10-kilometre-long version to capture satellites that have reached the end of their lives. However, the test will also explore some possible drawbacks. One concern is that the net will work very slowly, taking several months or even a year to de-orbit. Then there is the risk that the net will run into operational satellites. The engineers also worry that the debris they are fighting could fight back. “There is a possibility of the tether being severed by impacts of small debris objects or micrometeoroids,” says a JAXA spokesperson. Not everyone is convinced of the idea. A net isn’t necessarily the best option to collect debris, says Hugh Lewis, an aerospace engineer at the University of Southampton, UK. He has reservations about the net’s ability to deal with space junk. In particular, he believes it could actually generate debris if it collides with a large satellite. “There is a growing trend for organisations to put forward a concept for a debris removal device without considering fully the potential risks involved in deploying and operating the device,” says Lewis. “I believe that these ideas should be subjected to international scrutiny before they are deployed.”

Using a net is just one of the many proposed solutions to the orbital debris problem
• Sweep it up: A team at the Swiss Federal Institute of Technology in Lausanne is building a robot, CleanSpaceOne, to sweep up junk. It will deploy grippers inspired by jellyfish to embrace the target before steering itself on a suicide dive into Earth’s atmosphere.
• Drag it down: European aerospace company EADS Astrium wants to give satellites in-built sails to act as an “orbital brake”, dragging them into Earth’s atmosphere.
• Blast it away: Boeing wants to send up a rocket that could dispel the debris with blasts of inert gas. Others want to use lasers to clear the way.

A polar view of orbital debris. You can see how the debris is generally either in LEO (near the Earth) or GEO (farther away).An oblique view of the Earth showing space debris in both LEO and GEO, and Russia’s infatuation with north polar orbits.

With all those unruly satellites buzzing around above our heads, it’s about time someone stepped in to police all that space traffic. Or, at least provide a more accurate portrait of a satellite’s trajectory. Researchers from the Lawrence Livermore National Laboratory in California have developed a system of “space cops” – mini-satellites designed to track and refine a satellite’s path – that are better equipped to monitor low-orbit satellites and prevent collisions. The program, called the Space-Based Telescopes for Actionable Refinement of Ephemeris, or STARE, can predict a satellite’s trajectory to within less than 50 meters, according to initial tests. “Eventually our satellite will be orbiting and making the same sort of observations to help prevent satellite-on-satellite and satellite-on-debris collisions in space,” Lance Simms, lead author of a paper appearing in an upcoming edition of the Journal of Small Satellites, said in a statement. According to United States Space Surveillance Network, there are about 3,000 satellites currently operating in Earth’s orbit. Additionally, there are approximately 5,000 other man-made objects over 10 centimeters in diameter circling our planet.

That’s not to mention the millions upon millions of pieces of “space junk,” ranging in size from 10 centimeters to less than 1 centimeter, also whizzing around our planet, most of it traveling at speeds of up to 18,000 mph. In sum: There’s a lot of stuff up there moving really, really fast. The 2009 satellite collision above Siberia between two intact satellites is testament to how destructive a high-speed space crash can be (the satellites collided at a total speed of 26,170 miles per hour – neither satellite survived.) Satellite collisions, both with each other and with the surfeit of space debris currently orbiting Erath, are becoming increasingly problematic. As Earth’s satellite channels get clogged with junk, scientists must find better, more accurate ways to measure the trajectories of satellites traveling at thousands of miles per hour. According to Science Recorder, current technology can pinpoint a satellite’s location to within 1 kilometer. That level of uncertainty leads to about 10,000 false alarms for every confirmed collision, meaning satellite operators rarely follow up on collision warnings – until one actually occurs. Violent collisions are one thing, but experts also fear that space debris could at some point interfere with global positioning systems, international phone connections and television signals.

Researchers from the Lawrence Livermore National Laboratory in California hope to remedy that problem by sending a team of nano-satellites into low orbit to better monitor satellite traffic. The STARE mission aims to reduce the 1 kilometer window of uncertainty down to about 100 meters or smaller. Developers of the program hope to significantly reduce the number of In the case of the Livermore team, they were able to reduce the uncertainty to 50 meters, well below the 100-meter goal.

The U.S. Air Force’s decision to shut down a key component of its Space Surveillance Network will weaken the service’s ability to accurately detect and characterize objects in Earth orbit, experts say. The space fence shutdown, ordered by Gen. William Shelton, commander of Air Force Space Command, also will reduce the overall capacity of the system, these experts said. At the same time, they suggested it could increase pressure on the Air Force to award a contract on a next-generation system, which has stalled amid a Pentagon-wide review of its acquisition plans. According to two recent memos obtained by SpaceNews, the Air Force will shut down the aging Air Force Space Surveillance System, also known informally as the Space Fence, Sept. 1. The memos, from Austin Frindt, a contracting officer with Air Force Space Command, were addressed to Five Rivers Services of Colorado Springs, Colo., operator of the current Space Fence, which consists of a line of VHF radars stretching across the southern United States.

Deployed in the 1960s, the VHF Space Fence includes three transmitter sites and six receiving stations. It is responsible for approximately 40 percent of all observations performed by the Air Force-run Space Surveillance Network, which includes other ground-and space-based sensor assets, said Brian Weeden, technical adviser at the Secure World Foundation, a nonprofit organization dedicated to space sustainability. “The Space Fence does a lot of heavy lifting,” said Dave Baiocchi, a senior engineer at the Rand Corp., an Air Force think tank in Santa Monica, Calif. Without it, “you’re missing some level of accuracy,” he said. In a memo dated Aug. 1, Frindt said the Air Force was not exercising its option for a fifth year of a contract to provide management and logistical support for the nine field stations. Lori Thomas, president of Five Rivers Services, declined to comment and referred questions to the Air Force. “This is your notice to begin preparing the sites for closure,” the memo said. “A specific list of action items will be provided as soon as it is finalized.”

A follow-up memo dated Aug. 9 asked Five Rivers for an analysis of what it would cost to close the Space Fence sites. This memo said the system would be turned off Sept. 1. In an email Aug. 5 Andy Roake, a spokesman for Air Force Space Command, pointed to the automatic budget cuts known as sequestration. “In this tough, sequestered budget environment, we’re considering many options, but for FY14, no final decisions have been made,” he said. The memos suggest otherwise, asking for photographs of the closed sites, plywood on windows and weekly updates. Roake did not respond to follow-up questions by press time. A spokesman for the U.S. Strategic Command, which oversees the Joint Space Operations Center, referred questions to Space Command.

Though part of a broader surveillance network, the VHF Space Fence is crucial because it can track objects up to 24,000 kilometers away. Other ground-based sensors in the network generally track objects at altitudes lower than a few thousand kilometers, Weeden said. “The Space Fence is very important as it gives an ‘uncued tracking’ capability,” Weeden said. “Because it’s constantly transmitting, it can detect objects without being tasked to do so. There are some other sensors in the network that can do uncued tracking to some degree, but the Space Fence is rather unique in the sheer size of the detection coverage it has.” The Space Fence, along with operators at the Joint Space Operations Center, can observe objects down to the size of a basketball and make precise determinations of their characteristics, location and movement. Each month the system is responsible for logging more than 5 million observations of space objects, according to an Air Force fact sheet.

Experts said without the Space Fence, the Air Force will have a harder time knowing when orbital collisions have occurred. “It will be more difficult and take longer to detect and catalog new pieces of debris, especially those from large breakups,” Weeden said. “And the loss of capacity likely means that we have less accurate orbits for a good portion of the space debris” in low Earth Orbit, he said. In April, Shelton said two of the Space Fence’s receiver sites had been placed in cold storage, one in Glennville, Ga., and one in Hollandale, Miss., reducing the overall accuracy and effectiveness of the system. The change was made as part of the Air Force’s response sequestration, the across-the board-budget cuts that took effect in March. In July, the Air Force released a request for proposals to operate the aging system beginning in September 2015 — one year after the Five Rivers Services’ contract was set to expire. The request said the Space Fence “has been identified as a critical defense system and, therefore, shall be manned on a 24-hour, 7-days-a-week, 365-days-a-year basis at transmitter sites and 8-hour, 7-days-a-week, 365-days-a-year basis at receiver sites.” But as sequestration lingered, experts said, turning off the Space Fence may well have been the best of a bad set of options. Other sensors, they noted, have a dual mission that includes space surveillance and missile warning. “Closing them down would have impacted those other missions and likely generated a lot more political heat from Congress,” Weeden said.

Meanwhile, an overdue contract to build a next-generation Space Fence is on hold due to the Defense Department’s recently completed Strategic Choices and Management Review, which examined the Pentagon’s options under three different funding scenarios for the next decade. Baiocchi said he expected the closure of the current Space Fence to increase pressure on the Pentagon and Congress to fund a next-generation system, consisting of S-band radars, that would be capable of tracking golf ball-sized objects. Lockheed Martin Mission Systems and Sensors of Moorestown, N.J., and Raytheon Integrated Defense Systems of Tewksbury, Mass., have developed competing designs for the new Space Fence. Shelton said in July that engineers at Eglin Air Force Base in Florida were looking for ways to improve the current Space Fence as a contingency plan should the Pentagon elect not to go forward with the next-generation system.

More than 100 million objects orbit our planet, experts estimate, but only 1,134 of them are operational satellites. The rest is space junk: moribund satellites, discarded rockets, and millions of smaller pieces of debris, the result of in-orbit collisions. The Joint Space Operations Center—part of U.S. Strategic Command—tracks about 17,000 of the largest objects, including active satellites. Until now, little has been done to mitigate the space-junk problem, but two proposed missions could change that. DARPA’s Phoenix program would launch incomplete nanosatellites into space that could make themselves whole by harvesting working pieces from retired satellites. And CleanSpace One, a Swiss satellite due to launch in 2018, would clear low Earth orbit by directing debris into the atmosphere to burn up.